The invention relates to monolithically integrated semiconductor circuit arrangement, particularly for crosspoint arrays of switching systems, with semiconductor switching elements in matrix form arrangement, with intersecting input and output circuit paths, which may be connected together by means of switching elements, with control or triggering means for operating the switching elements and control or triggering lines from the control means to the switching elements.
Switching networks are common in communication technology for connecting a number of input and output lines. Conventional switching or connecting networks are predominantly constructed with mechanically or electromechanically operated switch contacts. Recently, switching networks were also known in which semiconductor elements are provided as switches.
Thus, for example, in German Auslegeschrift No. 1 298 188, an arrangement is described which is referred to as a switching network with electronic switching for telecommunications exchanges. The switching network comprises one or several connecting stages connected together via a link; the individual connecting stages in turn consist of several connecting matrices, and in which the switching of a transmission will be started by applying marking potentials to the columns and rows of the switching matrix. Such arrangements predominantly use four-layer elements as switches which have the property of being very low in impedance when connected, and when blocked have a low coupling capacity. In the cited application, reference is made to the fact that it is difficult to maintain the high decoupling values which are necessary for applications in telecommunications technology, with monolithic integration of several cross-points of a connecting matrix. In the above application, a rule is given as to how better properties of the elements may be achieved by additional changes in the semiconductor body, e.g. by changing the life span of the minority charge carrier.
A further development of such connecting matrices, particularly with respect to an improvement in the control or triggering possibilities, is described in German Auslegeschrift No. 1 812 542. By combining, in monolithic integration, the four-layer element forming a switch with a MOS element for control or triggering it is possible to achieve a high impedance characteristic for the control or triggering of the element. A particular speciality of these proposals may be seen in the control concept for such connecting matrices. The transmission path across the switching network may be built up automatically in the proposed arrangement and may be constructed with freedom of choice via several stages, if the two ends of the desired transmission path are marked. The cross-point elements ignite in an arbitrary manner and only the transmission path which is built up between the two marked ends may be maintained.
Another possibility for switching of telephone signals is described in DAS 2 033 647, which is based on the fact that MOS transistors are used as switches. In this application special control or triggering and logic processing circuits are for example proposed for control of switching matrices. Thus, the idea of combining the switching transistors to the control or triggering logic of the coupling matrix in the form of an integrated MOS circuit has already been mentioned.
Furthermore, from German Auslegeschrift No. 2 333 190 it known to design switching elements constructed as semiconductor switches for balanced transmission. Thus, the control electrodes of the two connection elements necessary for the construction of a connection should be connected and the control current should be supplied to this common line. In all previously known arrangements the disadvantage may be recognized that the requirement for a very high switching ratio, i.e. a very low resistance to connection and a very low residual coupling when disconnected, may only be achieved at additional expense.
Thus, of course, the degree of integration which may be achieved for switching elements with the desired properties, i.e. a forward resistance lower than approximately 10 ohms and "off"-attenuation greater than 100 dB, is very low. However, only very highly integrated switching matrices with a large number of crosspoints come into consideration for an economical solution in communication technology, because only in this manner may the lowest costs per crosspoint be produced.